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Compaction Baffle Filter

The Compaction Baffle (CB) Filter stands as a premier washing solution for removing dissolved solids for low production rate applications. With its compact, pressurized design, the CB's advantages over other types of washers include a minimum total installed cost, an environmentally-conscious totally-enclosed operation, the highest washing efficiency available, and simple, low cost maintenance. The CB Filter achieves greater capacities compared to other types of drum filters because it uses higher feed consistencies and operating speeds. This makes the CB Filter a relatively compact machine requiring much less building space than conventional vacuum or pressure washers, yet delivering superior performance.

The Efficient Combination

The production of chemical pulps requires several unit operations involving washing dissolved solids from the pulp. Several washing stages in a countercurrent series recover cooking chemicals in the brownstock or redstock washing systems, while bleach washers remove residual chemicals and adjust pH between bleaching stages. Washing of dissolved solids can be accomplished either by dilution/extraction or by displacement. The CB Filter delivers a combination of the two operations in one machine. This is important because the dilution/extraction step helps to release dissolved solids trapped within the fibers, allowing the displacement step to remove this material from within the pulp matrix. This combination makes the CB Filter an efficient washer at a low cost per ton of production

A Cycle of Innovation

  • Tapered Inlet Box and Deflocculating Slice - Provides uniform basis weight and excellent sheet formation across the full length of the machine.
  • Formation Zone - Entering pulp slurry is dewatered through the perforations in the rotating drum and becomes the pulp mat.
  • Compaction Zone - The pulp sheet is gently compressed by the primary and compaction baffles. Strong liquor from the pulp sheet is expressed through the perforations in the drum until the consistency is approximately 20%, completing the dilution/extraction portion of the wash cycle.
  • Displacement Zone - The pulp emerges from the tip of the compaction baffle into the lower wash pond. Displacement wash liquor passes Airlift Take-Off.
  • Drying Zone - The pulp sheet rises out of the upper wash pond and is carried over the top of the cylinder where the hood overpressure dries it to a high consistency prior to discharge from the machine.
  • Air Lift Take-Off - A timing valve at the filtrate discharge end of the machine equalizes the pressure across the surface of the cylinder, allowing the pulp sheet to be positively removed by the air lift take-off assembly.
  • Crumb Sluice Chamber and Cylinder Cleaning Showers - The chamber between the air lift take-off and the inlet box is known as the crumb sluice chamber. Blower air enters here to lift the pulp mat and to simultaneously provide the hood overpressure. This chamber contains the high and low pressure cleaning showers.
  • Pressurized Repulper - No sealing device is needed between the cylinder and the pulp discharge, reducing maintenance costs and downtime. The repulper can also function as a built-in steam mixer for certain processes requiring higher pulp temperatures. The washed stock discharges to either a pressurized chamber or a thick stock pump.

Principle of Operation

In operation, stock is delivered to the washer through a tapered inlet box. To maintain a uniform flow and pressure along the length of the inlet box, a small quantity of stock (10%) recirculates from the narrow end and returns to the pulp stream ahead of the washer or back to the previous feed tank.

From the inlet box, stock enters the vat through a deflocculating slice concurrently with the drum rotation. The pulp forms a mat on the rotating drum and is compacted to high consistency by the primary baffle. This compaction expresses strong liquor from the pulp prior to displacement washing.

A unique hydrodynamic baffle separates the feed section of the vat from the wash liquor pond. Wash liquor is displaced through the pulp mat by the force of the constant pressure in the sealed hood. This provides uniform flow of wash liquor through the mat resulting in higher washing efficiencies than can be achieved by conventional showers. Washed stock is removed from the washer cylinder by means of an airlift take-off into a pressurized breaker/conveyor.

Hood pressure is maintained by a small blower, which recirculates vapor from the filtrate tank in a closed circuit. Filtrate from the pulp flows horizontally from the washer valve to a filtrate tank. There is no liquor cascading from the washer to the tank to entrain air and generate foam, resulting in much smaller filtrate tanks.

  • Excellent washing efficiency
  • Low steam and power consumption
  • Easy operation and good runnability
  • High availability
  • Small installation footprint and height requirements
  • Minimum amount of piping
  • Easy maintenance and Accessibility
  • Suitable for system rebuilds, upgrades and modernizations

Feature Benefit
Deflocculating Slice Assures excellent mat formation through a wide range of inlet consistencies and production rates. 
Hydrodynamic Baffle Creates a gentle converging zone to extract the dirty liquor from the newly formed pulp mat. 
Continuous Wash Pond Provide nearly perfect flow of wash liquor through the compacted mat. 
Permanent Filtration Medium Finely drilled stainless steel decking plate replaces winding wires, backing wires, face wires and acme bands.
Closed Vapor Loop Vapors from the filtrate tank are recirculated to the washer by a positive blower. 
Pressurized Design Eliminates the need for long drop legs and thus allows for low level installation. 
Totally Enclosed Eliminates the possibility of stock spills and contains noxious and toxic vapors. 
Fully Automatic Instrumentation provides all operating data allowing remote operation and control. 



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